Sampling device for ph measurement in process streams



Nov. 4, 1958 c. E. MlcHELsoN' ET AL 2,859,164

SAMPLING DEVICE FOR PH MEASUREMENT IN PROCESS STREAMS Filed April 1o.1957 v S 2 sheets-sheet 1 Hi tof/z e/y Nov. 4, l1,958 c. E. MICHELsoN,ETAL 2,859,154

SAMFLING DEVICE FOR PH MEASUREMENT IN PROCESS STREAMS Filed April 1o;1957 2 Sheets-Sheet 2 I -INVENTORS william M Carson, zf: BY

III'I wsw IML.

United States Patent O "ice SAMPLING DEVCEFR pH MEASUREMENT IN PROCESSSTREAMS Christian E. Michelson" and William N. Carson, Jr., Scotia, N.Y., assignors to the United States of America as represented by theUnited States Atomic Energy Commission Application April 10, 1957,Serial No. 652,072

3 Claims. (Cl. 204-195) This invention relates Vto the measurement ofthe hydrogen ion content in process streams and, more particularly, to anovel apparatus for continuously monitoring process streams wherein therecorded results obtained by the apparatus not only indicate thehydrogen ion content of the process stream but also indicates the properfunctioning of the apparatus.

This invention isV particularly useful in monitoring process streamswhere accessibility to the monitoring apparatuses is limited. Thesimplicity of the apparatus of this invention plus the malfunctionindicating feature make it particularly adaptable to monitoringradioactive streams where the sampling equipment must be shielded forthe protection of human beings.

An object of this invention isto provide an apparatus for the reliablemeasurement of the hydrogen ion concentration in process streams.

Another object of'this invention is to provide a reliable apparatus formeasuring' the hydrogen ion concentration in process streamsv whichwilll operate without constant operator attention and is easy tomaintain.

Another object of this invention is to provide a reliable apparatus'formeasuring thehydrogen ion concentration in process streams' inwhichmalfunctions due to clogging by deposits in thel process stream arereduced to a minimum.

Still another object of this invention is toprovide an apparatus for thereliable measurement of the hydrogen ion concentration ofprocess streamswherein the recorded results obtained by the apparatus indicates theproper functioning of the apparatus.

It is anotherobject' of this invention to provide an apparatus for thereliable measurement of the'hydrogen ion concentration in processstreamswhich is provided with an automatic means for standardizing theequipment to maintain an accuratel measurement of the uids passedtherethrough.

Further objects and advantages of the invention will be evident from thefollowing description of an exemplary embodiment.

Referring to the drawings:

Figure 1 is a diagrammatic view illustrating the monitoring apparatus ofthe present invention.

Figure 2 is a sectional view of a pH cell constituting part of themonitoring apparatus.

Figure 3 is 4a view illustrating the electric circuit of theflush-control unit.

The system shown in Figure l is particularly adapted for use inmonitoring the hydrogen ion concentration of a radioactive processstream such `as is shown owing in a process Vessel10. A vacuum pump 11comprising an air nozzle or jet 12, a vacuum chamber 13 and a dischargepipe 14 to theprocess vessel 10, is connected throughl a bayonet sampler15 to a pipe 16, serving as an intake through a pipe 17 and a manuallyoperated valve 18 to a pH cell 19. The bayonet sampler 15 is iitted'witha long neck 20 and capped by stopper 21 to provide an access for takingprocess stream samples 2,859,164 Patented Nov. 4,- 1958 from the device.A source 21a of high-pressure air is connected through pipe 22 to theintake pipe-16 at a point between the process vessel 10 and the junction23. This side arm location causes the bottom portion of the glass cup toform a reservoir 25 permitting trapping of samples of the process streamwhich enter the pH cell through the side arm 24. A glass electrode 26and a reference electrode 27 arev sealed into the cell 19 by means of acold-setting plastic cap 28. The glass electrode 26 contains the usualinternal solution 29 which is connected to the usual output lead 30. Thereference electrode 27 is formed of saturated calomel having a saltbridge in its bottom portion fabricated of a porous glass to ensure lowelectrolyte flow therein. A suitable glass for this use is one having adry density of 1.45 gm./cm.3, void spaces of 28% of the volume, anaverage pore diameter of v4 millimicrons, a ow rate of .00065cc./cm2/br. at 2 mm. thickness for water applied thereto at oneatmosphere pressure, and the following composition in weight percent:

The electrodes 26 and 27 extend into the glass cup 23 far enough thattheir lower ends lie just below the level of the uid retained in thereservoir 25 so as to be constantly immersed therein. A flush tube 33leads into the pH cell 19, through which buler and ilush solutions areintroduced. Aground wire 34 is provided in the assembly to ensureconstant electrical grounding' of the sample. As shown in Figure l, theelectrode leads 30 and 32 are electrically connected to a pH meter 35which is located behind a radiological shield 36. A recorder Y 37 isconnectedgto the pH meter 35 for constantly recording in permanent formthe results obtained by the pH cell 19. The pH meter 35 may be of anystandard type such as the Beckman RX pH meter, and the recorder may takeany form;however a circular chart type recorder, such as a Foxbororecorder, was found advantageous.

The sampling system hereinbefore described operates in the followingmanner. When the jet 12 is turnedron, the passage of air therethroughcreates a. vacuum in the vacuum chamber 11', the bayonet sampler 15, thepH cell, and pipes 16 and 17. When the vacuum is suiiiciently high, uidrises in the pipe 16. Air from the source 21a is also introduced intothe pipe y16 through the pipe 22, causing the fluid risinginpipe`16 tobe mixed with bubbles of air. The air and uid yare circulated throughthe sampler 15`into the vacuum chamber 11 and back into the processvessel 10. The air introduced into the pipe 16 causes the iluid thereinto rise in intermittent slugs, thereby continually changing the vacuumin the pH cell 19, pipe' 17, bayonet sampler 15, and the vacuum chamber11. When the system is full of lluid, the vacuum is greatest, but, whenVan air bubble enters, the vacuum is reduced. Sample uid leaves thepHcell 19 when the vacuum is greatest, and enters when the vacuum isreduced. A portion of the sample, however,

always remains in the reservoir portion 25 of the pH water hose toremove any obstructions which may be causing a malfunctioning of thedevice.

A ush reservoir 38 containing a wash solution of predetermined pH valuesubstantially dilferent ornl the range of pH values of the processstream Huid, is connected through an automatically controlled valve 39,hereafter called a tiush valve, to the inlet tube 33. A source of air39a is also connected to the inlet tube 33 through another automaticallycontrolledvalve 40 hereafter called a vent valve. The air and the washsolution are admitted to the pH cell 19 through the inlet tube 33 at 10minute intervals to flush the system, thereby lessening the malfunction`by clogging from any foreign matter in the process stream. The meter 35and recorder 37 measure and record the pH value of the wash solution atlO'minute intervals, ,thereby indicating the proper functioning of theapparatus. It will be noted that a steadyreading of the pH value of theprocess stream with no peaks to the pH value of the wash solutionindicates a malfunction somewhere in the wash solution introducingmechanism while a steady reading of the pH value of the wash solutionwould indicate a breakdown of the process stream introducing mechanism.The valves 39 and 40 are automatically controlled by the ush-controlunit 41 hereinafter described.

A buer reservoir 42 is also connected to the inlet tube 33 through athird automatic valve 43 hereafter called a buler valve. The buffer uidstored in the reservoir. 42 is of a predetermined pH value and is usedto standardize the system. The butler uid is automatically introducedinto the pH cell once every hour, and its measured pH value is noted onthe recorder. Any deviations from the recorded pH value of the butferfrom the known pH value of the buffer solution are used as a correctionfactor on the readings for the process stream samples being measured.The automatically controlled valve 43 for the butfer reservoir 42 isalso controlled by the Hush-control unit 41. Y

The Hush-control unit 41 is employed to operate the valves 39, 40, and43 to admit the bulfer and ush solutions and air. Figure 3 showsdiagrammatically the wiring scheme for the flush-control unit 41. Asource of power, not shown, is connected to a motor 44 through fuses 45and manual switch 46, `indicator light 47 being lit when the manualswitch 46 is in its closed position. The motor 44 is operated at $60 ofa revolution per minute; cams 48 and 49 are drivingly connectedtherewith in a two-to-one ratio so that they make a complete revolutiononce every two hours. The motor 50 operates at lo of a revolution perminute and cams 51 and 52 are drivingly connected therewith at aone-to-one ratio so that they make one complete revolution every tenminutes.

To describe the operation of the flush-control unit 41, let it rst bevassumed that cams 48 and 49 are revolved to a position vsuch thatswitches 53 and 54, respectively,

are actuated to their upper positions. Power is then being supplied tothe 3A0 R. P. M. motor 50 through lines 55, switch 53, and line 56.lWhen the lo R. P. M. motor 50 rotates to a certain point,cams 51 and52. also rotate to a certain point such that switches 57 and 58,respectively, drop to their lower positions. In the lower position ofswitch 57 power is supplied to a coil 59 for the vent valve` 40 throughline 60, switch 57, and line 61. In the lower position of switch 58power is delivered to a coil 62 for the ush valve 39 through line 63,switch 54, line 64, switch 58, and line 65. The supply of power to thevent-valve coil 59 and ush-valve coil 62 causes them to open, admittingair and wash solution tothe sampler through the inlet tube 33. Theamount of air supplied is sufficient to reduce the vacuum in the samplersystem to the point wherecirculation of process stream sample isstopped. The wash solution replaces the process uid in the reservoir 25of the pH cell 19 and the pH meter 35 reads the pH of the wash solution.As the lo R. P. M. motor 50 continues to r0tatecam 52 actuated yQ @useswitch 58 to return to its upper position, thereby cutting off power tothe ush-valve coil 62 causing the ush valve j However, the vent valve 40stays open `for an additional 15 seconds allowing the wash solution to.

39 to close.

be cleared from the inlet tube 33. Upon the removal of power from coil59 by the operation of cam 51 returning switch 57 to its upper position,the vent valve 40 Y' closes, the system becomes vacuum tight, and thejet 12 .Y

will again be able to pull process stream fluid from the processstreamtank 10. This ush operation is repeated every 10 minutes. f Y

When the 1,60 R. P. M. motor 44 rotates far enough to start thestandardization cycle, cam-48'will cause switch 53 to drop to its lowerposition thereby Yremoving power along one path to the lyo R. P. M.motor 50. f However, the %0 R. P. M. motor 44 continues to receive?power through line 55, line 60, and switch 57, which is 1 in its upperposition, until the Hush cycle is reached, atl which time power isremoved from the 3A0 R. P. M.

motor 50 and the cams 51 and 52 stop rotating. The 1 vent-valvecoil S9and the flush-valve coil 62 are energized and their respective valves4t? and 39 are heldopcn tiushing the pH cell 19 until cam'49 operates kto cause switch 54 to drop to its lower position at which time power` isremoved from the flush-valve coil .62 and is supplied to thelbutler-Valve coil 66-through line 55, line 63, switch 54 in its lowerposition, and line 67. 'I'hefbutervalvev 43 operates so that the buerfluid plus `the air stream values for that iluid. The buffer solution`ows for a` period of one minute at'which time cams 48 and 49 operate toreturn their respective switches 53 and 54 to their upper positions.Switch 54 Vcuases Vthe powerto be cut off from the buffer-valve coil 66and reapplied tothe lush-valve coil 62. 'The operation of switch 53causes power to be again supplied to the -/l'R. P. M. motor 50 causingthe control unit 41 to continue with the ush Y cycle. The buffer cycleis repeated every two hours.

The materials used in the constituentV parts of this sampling device arenot critical. VIt: isnecessary only that the materials used bechemically inert to the process j,

stream uid, the iushorvwash uids, and the buier uids..

It is recommended that the Vwash solution used the'. device be acidic incontent if the process stream tluid being monitored is alkaline, or viceversa.y AThe, buffersV solution would best be on the alkaline side ifthestream is so.

Various changes and modifications can be. made withprocess outdeparting'om the spirit of the. invention as delned in the appendedclaims. v

What is claimed is:

1. A device for monitoring4 the hydrogen 4ion .concert-.Y

tration of the uid in a process stream comprising2 a pH cell having itsbottom end forming a shallow reservoir and adapted to generate anelectric current proportional to the pH value of a Huid in thereservoir, a process vessel for containing the Aprocess stream, .anintake line between the vessel and the pH cell, a jet operated vacuumpump connected to the-intake line for causing fluidy to flow in theintake line, an air supply connected .to the,

intake line between the vessel and the pump for causing samples ofprocess stream tluid to intermittently flow into and out of the pH cell,a portion ofthe process stream remaining in the reservior, aninletto'the pH cell, means for introducing air into the pH. cellthroughthe inlet to stop the ow of process stream fluid into the. pHcell, means for introducing a wash solution fluid of predetermined pHvalue substantially' different from therange of values of the processstream intothe pH Vcell 5 through the inlet, cam driven means forcontrolling the air introducing means and the Wash fluid introducingmeans to replace the process stream fluid in the reservoir therewith atpredetermined intervals, and means electrically connected to the pH celland responsive to the electric current generated therein forcontinuously measuring and recording the pH of the uid in the reservoirwhereby a constant recording of the pH value of the wash ud wouldindicate a failure of the sample introducing means and a constantrecording of the pH value of the process stream iluid Would indicate afailure of the replacing means.

2. A device as dened in'claim 1 comprising means responsive to thecontrol means for periodically introducing a buler solution uid into thepH cell through the inlet for use in standardizing the device.

3. A device for monitoring the hydrogen ion concentration of the uid ina process stream comprising a pH cell, said pH cell having a processstream lluid entry adjacent the bottom end thereof, a reservoir forprocess stream uid formed at the bottom of said pH cell below saidentry, a process vessel below said pH cell containing the process streamliuid, an intake line between the vessel and the entry to said pH cell,a pressurized air supply connected to said intake, a jet operated vacuumpump making connection with the intake line between the pH cell entryand the pressurized air connection whereby the process stream uidintermittently ows into and out of the reservoir in the pH cell.

References Cited in the le of this patent UNITED STATES PATENTS1,684,645 Smith et al Sept. 18, 1928 2,396,934 Wallace Mar.v19, 19462,607,718 Suthard Allg. 19, 1952 2,758,079 Eckfeldt Aug. 7, 19562,782,151 Suthard Feb. 19, 1957

1. A DEVICE FOR MONITORING THE HYDROGEN ION CONCENTRATION OF THE FLUIDIN A PROCESS STREAM COMPRISING, A PH CELL HAVING ITS BOTTOM END FORMINGA SHALLOW RESERVOIR AND ADAPTED TO GENERATE AN ELECTRIC CURRENTPROPORTIONAL TO THE PH VALUE OF A FLUID IN THE RESERVOIR, A PROCESSVESSEL FOR CONTAINING THE PROCESS STREAM, AN INTAKE LINE BETWEEN THEVESSEL AND THE PH CELL, A JET OPERATED VACUUM PUMP CONNECTED TO THEINTAKE LINE FOR CAUSING FLUID TO FLOW IN THE INTAKE LINE, AN AIR SUPPLYCONNECTED TO THE INTAKE LINE BETWEEN THE VESSEL AND THE PUMP FOR CAUSINGSAMPLES OF PROCESS STREAM FLUID TO INTERMITTENTLY FLOW INTO AND OUT OFTHE PH CELL, A PORTION OF THE PROCESS STREAM REMAINING IN THE RESERVOIR,AN INLET TO THE PH CELL, MEANS FOR INTRODUCING AIR INTO THE PH CELLTHROUGH THE INLET TO STOP THE FLOW OF PROCESS STREAM FLUID INTO THE PHCELL, MEANS FOR INTRODUCING A WASH SOLUTION FLUID OF PREDETERMINED PHVALUE SUBSTANTIALLY DIFFERENT FROM THE RANGE OF PH VALUES OF THE PROCESSSTREAM INTO THE PH CELL THROUGH THE INLET, CAM DRIVEN MEANS FORCONTROLLING THE AIR INTRODUCING MEANS AND THE WASH FLUID INTRODUCINGMEANS TO REPLACE THE PROCESS STREAM FLUID INTRODUCING THEREWITH ATPREDETERMINED INTERVALS, AND MEANS ELECTRICALLY CONNECTED TO THE PH CELLAND RESPONSIVE TO THE ELECTRIC CURRENT GENERATED THEREIN FORCONTINUOUSLY MEASURING AND RECORDING THE PH OF THE FLUID IN THERESERVOIR WHEREBY A CONSTANT RECORDING OF THE PH VALUE OF THE WASH FLUIDWOULD INDICATE A FAILURE OF THE SAMPLE INTRODUCING MEANS AND A CONSTANTRECORDING OF THE PH VALUE OF THE PROCESS STREAM FLUID WOULD INDICATE AFAILURE OF THE REPLACING MEANS.